1. Field of the Invention
The invention relates to a method of fabricating a semiconductor device and, more particularly, to a method of fabricating an inductor that has high inductance, has high quality factor (Q) and may be designed under the same design environments as logic devices.
2. Description of the Related Art
In general, an SOC (System-on-a-Chip), which is referred to as an LSI (Large Scale Integrated circuit) system or an IC (Integrated Circuit) system, is obtained on one chip by integrating a system that has been constructed on a PCB (Printed Circuit Board) using a single semiconductor. That is, an SOC is a chip having complete and operable products thereon. For example, an SOC used in communication includes a microprocessor, DSP (Digital Signal Processor), RAM (Random Access Memory) or ROM (Read Only Memory). When using such an SOC, the size of the system further decreases and the assembling process becomes simplified.
In an SOC, a conventional semiconductor device and an RF (Radio Frequency) circuit device can be obtained on one chip. The mixed signal circuit used in the RF range follows the trend of being formed on a silicon-based semiconductor substrate. Such a circuit includes basic passive devices, such as resistors, capacitors, and inductors.
In particular, an inductor, which has the largest area among the passive devices, should have high performance, that is, high inductance (L) and quality factor (Q) determining its ability to accumulate energy. As the quality factor (Q) increases, the frequency properties of a voltage-controlled oscillator and a band pass filter are stabilized and the loss from these components decreases.
In an inductor, inductance is determined by the length of the metal wire of the inductor, and also the quality factor (Q) depends upon the resistance of the metal wire. However, in the uppermost metal wire, used as the inductor in an RF CMOS (Complementary Metal Oxide Semiconductor) process or a general logic process, it is difficult to sufficiently extend the length of the metal wire due to the limited area of the chip. Further, the thickness of the metal wire is insufficient due to the limitations of the process. Therefore, the resistance of the inductor increases to result in a low quality factor (Q).